Controller and method for managing economizer outputs

ABSTRACT

There are disclosed controllers and methods for managing economizer outputs. The economizer controller comprises an input component, a processor, and an output component. The input component receives incoming control signals from an input device, in which each incoming control signal is associated with a corresponding compressor. The processor generates an altered association of some of the incoming control signals to a different compressor based on a predetermined criteria. The output component sends output control signals based on the altered association to a control circuit associated with the compressors.

FIELD OF THE INVENTION

This application relates to the field of environmental control systemsand, more particularly, to system operation of fresh air intakecomponents of HVAC units.

BACKGROUND

An environmental control system of a building manages heating,ventilation, and air conditioning (HVAC) components to manageenvironmental conditions within the building. The system may include aneconomizer may allow fresh air external to the building to circulatethrough the HVAC components and cool the environmental conditions of thebuilding in an efficient manner. Referring to FIG. 1, there is shown aprior art air-side economizer 100 published by the U.S. Department ofEnergy as a representative Energy Star product. The HVAC components ofthe conventional economizer 100 include heating and/or cooling coils102, 104 that modify, if necessary, the temperature of return air 106 togenerate supply air 108 for the building. The economizer includes anoutside air damper 110 controlled by an outside motorized actuator 112via an outside linkage 114 to manage the amount of outside air 116entering the system and a return air damper 118 controlled by a returnmotorized actuator 120 via a return linkage 122 to manage the amount ofreturn air 106 continuing through the system. A logic controller 124 ofthe economizer controls the outside and return motorized actuators 112,120 based on an outside temperature sensor 126 to manage the mixed air128, i.e., mixture of outside air and return air, circulated through thesystem.

Although economizers have the potential to save substantial energy formaintenance of buildings, many existing economizers fail to providesignificant cost savings. At least part of the problem may be attributedto the current design of rooftop units having multi-stage coolingcapacity. For instance, an economizer may operate one compressor basedon a cooling stage 1 signal received from the thermostat, anothercompressor based on a cooling stage 2 signal received from thethermostat, and so on. For conventional rooftop units, cooling stage 1is the primary cooling capacity that runs at both full load and partialload. The other cooling stages are more secondary and subsequent, thusprovide cooling capacity to meet higher or peak demand such that theyrun less often. Over time, the run time imbalance among the multiplestages becomes more significant so the compressors wear out unevenly,i.e., the primary compressor wears out sooner than the othercompressors. Also, when a primary compressor wears out, the entirerooftop unit is typically replaced (instead of just the worn compressor)so the overall unit lifetime is unacceptable and the repair/replacementcost remains high.

SUMMARY

In accordance with one embodiment of the disclosure, there is provided arotational approach of economizer outputs for building managementsystems.

One aspect is a controller for managing of economizer outputs comprisingan input component, a processor, and an output component. The inputcomponent is configured to receive incoming control signals from aninput device, in which each incoming control signal is associated with acorresponding compressor. The processor is configured to generate analtered association of some of the incoming control signals to adifferent compressor based on a predetermined criteria. The outputcomponent is configured to send output control signals based on thealtered association to a control circuit associated with thecompressors.

Another aspect is a method of a controller for managing economizeroutputs. Incoming control signals are received from an input device, inwhich each incoming control signal is associated with a correspondingcompressor. An altered association of some or all of the incomingcontrol signals to a different compressor are generated based on apredetermined criteria. Output control signals are sent based on thealtered association to a control circuit associated with thecompressors.

Yet another aspect is a non-transitory computer readable mediumincluding executable instructions which, when executed, causes at leastone processor to manage rotation of economizer outputs. Incoming controlsignals are received, in which each incoming control signal isassociated with a corresponding compressor. An altered association ofsome or all of the incoming control signals to a different compressor isgenerated based on a predetermined criteria. Output control signals aresent based on the altered association.

The above described features and advantages, as well as others, willbecome more readily apparent to those of ordinary skill in the art byreference to the following detailed description and accompanyingdrawings. While it would be desirable to provide one or more of these orother advantageous features, the teachings disclosed herein extend tothose embodiments which fall within the scope of the appended claims,regardless of whether they accomplish one or more of the above-mentionedadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, wherein likenumbers designate like objects.

FIG. 1 is a partial perspective view of a rooftop unit known in the art.

FIG. 2 is a schematic representation of an economizer controller in anexample implementation that is operable to employ techniques describedherein.

FIG. 3 is a planar view with input/output representations of an exampleembodiment of the economizer controller of FIG. 2.

FIG. 4 is a block diagram representing an example implementation of theinternal components of the economizer controller of FIG. 2.

FIG. 5 is a flow diagram representing an example operation of theeconomizer controller of FIG. 2.

FIG. 6 is an abstract view representing an example operationalinformation about cooling and/or heating components associated with theeconomizer controller.

DETAILED DESCRIPTION

Various technologies that pertain to systems and methods that facilitaterotation of economizer controller outputs for heating, ventilation, andair conditioning (HVAC) components will now be described with referenceto the drawings, where like reference numerals represent like elementsthroughout. The drawings discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged apparatus. It is to be understoodthat functionality that is described as being carried out by certainsystem elements may be performed by multiple elements. Similarly, forinstance, an element may be configured to perform functionality that isdescribed as being carried out by multiple elements. The numerousinnovative teachings of the present application will be described withreference to exemplary non-limiting embodiments.

An economizer controller manages free cooling, mechanical cooling, orboth, depending on environmental air conditions. The economizercontroller also routes the cooling and/or heating demands, representedby signals from an input device (such as a thermostat), to economizercontroller outputs corresponding cooling and/or heating components ofthe HVAC unit or rooftop unit. Examples of economizer controller outputsinclude Y1-Out, Y2-Out, Y3-Out, etc. in the case of cooling components(such as compressors for cooling), or in the case of heating components(such as compressors for heating) in heat pump configuration. For someembodiments, the economizer controller may route the cooling and/orheating commands based on a start/stop order stored at the controllerand/or determined by a device remote from the controller. Conventionalcooling systems have fixed compressor priority for cooling systems inwhich Y1-Out always corresponds to primary compressor #1, Y2-Out alwayscorresponds to compressor #2, etc., and the staging logic would bealways first-in and last-out, which causes the primary compressor withhigher priority to wear excessively. In contrast, the economizercontroller adjusts the priority of cooling and/or heating components torotate utilization of these components and maximize their longevity.

Referring to FIG. 2, there is shown a schematic representation 200 of aneconomizer controller 210 in an example implementation that is operableto employ techniques described herein. Although other components may beincluded in the example implementation, the schematic representation 200has been simplified (omitting certain components) to facilitate generalunderstanding of the economizer controller 210 and its operation. Theeconomizer controller 210 communicates with an input device 220, such asa thermostat, as well as a control component 230 of the HVAC unit orrooftop unit, such as a terminal board. The economizer controller 210also communicates with other devices of the HVAC unit and/orenvironmental control system via HVAC control lines 240.

Among other functions, the economizer controller 210 receives coolingand/or heating signals 250 from the input device 220, prioritizes theincoming signals based on a predetermined criteria 260, and routes theprioritized outgoing signals 270 to the control component 230 of theHVAC unit or rooftop unit. For embodiments where the economizercontroller 210 resorts and routes signals for cooling components, suchas compressors for cooling, the incoming signals 250 may be designatedand Y1, Y2, and the like, and the outgoing signals 270 may be designatedsimilar as Y1, Y2, and the like. For some embodiments, the number ofoutgoing signals 270 may equal the number of incoming signals. Thepredetermined criteria may be based on, but not limited to, run timedata, cycle count data, availability information, and/or otheroperational information about cooling and/or heating components of theHVAC unit

It is to be noted that the process of resorting and rerouting results inone or more incoming signals being assigned to a cooling and/or heatingcomponent different from the component that may have been intended bythe input device 220. For example, the input device 220 may haveprovided an incoming signal Y1 to the economizer controller 210 for thepurpose of operating a first compressor of the cooling system. However,the economizer controller 210 may prioritize the other incoming signalsY2, Y3, and Y4 higher than incoming signal Y1, such that incoming signalY2 is designated as outgoing signal Y1 to operate the first compressor,incoming signal Y3 is designated as outgoing signal Y2 to operate asecond compressor, and incoming signal Y4 is designated as outgoingsignal Y3 to operate a third compressor. As a result, incoming signal Y1is designated as outgoing signal Y4 to operate a fourth compressor.Thus, by adjusting the priority and usage of the cooling and/or heatingcomponents, the economizer controller 210 may rotate utilization ofthese components and maximize their longevity.

The control component 230 may also bypass the economizer controller 210and communicate directly with the input device 220 via control lines280. For example, for some embodiments, the cooling demand signals Y1,Y2, etc. may be managed by the economizer controller 210 whereas theheating demand signals W1, W2, etc. may be provided to the controlcomponent 230 by the input device 220.

Referring to FIG. 3, there is shown a planar view with input/outputrepresentations of an example embodiment 300 of an economizer controller302. The economizer controller 302 is an example representation of theeconomizer controller 210 of FIG. 2, and the economizer controller iscoupled to an input device, such as a thermostat 304, and a terminalboard 306 of the HVAC unit or rooftop unit (represented by FIG. 1). Inparticular, some ports of the thermostat ports 308 of the thermostat 304are coupled to input ports 310 of the economizer controller 302, andsome ports of the terminal ports 312 of the terminal board 306 (of theHVAC unit or rooftop unit) are coupled to the output ports 314 of theeconomizer controller. The economizer controller 302 may manage routingof cooling components via connections Y1, Y2, and the like, and heatingcomponents via connections W1, W2, and the like. For example, formanagement of cooling components (such as compressors for cooling) asrepresented by FIG. 3, thermostat ports 308 for Y1 and Y2 are connectedto input ports 310 for Y1I and Y2I, respectively, of the economizercontroller 302. Similarly, output ports 314 of the economizer controllerare coupled to some ports of the terminal ports 312 of the terminalboard 308. For example, as shown in FIG. 3, output ports 314 for Y1O andY2O are connected to terminal ports 312 for Y1 and Y2, respectively, ofthe terminal board 306. Although FIG. 3 shows W1 and W2 of thethermostat ports 308 coupled directly to W1 and W2 of the terminal ports312, W1, W2, and the like of the thermostat ports and the terminal portsmay connect to the input and output ports 310, 314 of the economizercontroller 302 for other embodiments where heating components aremanaged. Also, a power source 316, such as a 24 volt transformer, may beconnected to the ports 308, 310, 312, 314 of the economizer controller302, the thermostat 304, and/or the terminal board 306.

As noted above, the economizer controller 302 manages free cooling,mechanical cooling, or both, depending on environmental air conditions.Thus, the economizer controller 302 may be coupled to other componentsof the HVAC unit or rooftop unit as well. Examples of the othercomponents includes, but are not limited to, mixed-air temperatureand/or discharge-air temperature devices 318, outdoor air temperaturenegative temperature coefficient devices 320, and damper actuators 322.

FIG. 4 represents an example economizer controller 400 of anenvironmental control system. The economizer controller 400 may be anytype of controlling device that is capable of managing cooling and/orheating of a designated area and routing cooling and/or heating demandsfrom a thermostat signal to an HVAC unit having multi-stage coolingand/or heating capacity. An example of an economizer controller 400 is,but are not limited to, a direct digital controller (DDC) capable ofcompressor rotation for cooling components of the HVAC unit. Theeconomizer controller 400 comprises a communication bus 402 forinterconnecting the other device components directly or indirectly, oneor more processors 406, and one or more memory components 408.Optionally, some embodiments of the economizer controller 400 may alsoinclude a communication component 402 for wired or wireless connectionto a mobile device and/or a memory-based drive.

The one or more processors 406 may execute code and process datareceived at other components of the economizer controller 400, such asinformation received at the communication component 404 or stored at thememory component 408. The code associated with the economizer controller400 and stored by the memory component 408 may include, but is notlimited to, operating systems, applications, modules, drivers, and thelike. An operating system includes executable code that controls basicfunctions of the economizer controller 400, such as interactions amongthe various components of the economizer controller, communication withexternal devices via the communication component 404, and storage andretrieval of code and data to and from the memory component 408. Eachapplication includes executable code to provide specific functionalityfor the processor 406 and/or remaining components of the economizercontroller 400. An example of an application executable by the processor406 includes, but is not limited to, a resorting logic 410 based on runtime data, cycle count data, availability information, and/or otheroperational information about cooling and/or heating components of theHVAC unit. Data is information that may be referenced and/or manipulatedby an operating system or application for performing functions of theeconomizer controller 400. Examples of data associated with theeconomizer controller 400 and stored by the memory component 408 mayinclude, but are not limited to, the operational information aboutcooling and/or heating components of the HVAC unit 412 utilized by theresorting logic, an initial matrix of incoming thermostat signals 414,and a new matrix of cooling and/or heating demand 416 by routing theincoming thermostat signals.

The economizer controller 400 may further comprise one or more inputcomponents 418 and one or more output components 420. A user interface422 of the economizer controller 400 may include portions of the inputand output components 418, 420 and be used to interact with a user ofthe economizer controller. For example, the user interface 422 mayinclude a combination of hardware and software to provide a user with adesired user experience. The input and output components 418 and 420 mayinclude ports for receiving incoming signals from a thermostat orsending outgoing signals to a cooling and/or heating component of anHVAC unit. Examples of the ports of the input components 418 forreceiving incoming signals include, but are not limited to, a Y or Y1input port 424, aY2 input port 426, a Y3 input port 428, and/or a Y4input port 430. Examples of ports of the output components 420 forsending outgoing signals include, but are not limited to, a Y or Y1output port 432, a Y2 output port 434, a Y3 output port 436, and/or a Y4output port 438.

It is to be understood that FIG. 4 is provided for illustrative purposesonly to represent examples of the internal components of the economizercontroller 400 and is not intended to be a complete diagram of thevarious components that may be utilized by the device. Therefore, theeconomizer controller 400 may include various other components not shownin FIG. 4, may include a combination of two or more components, or adivision of a particular component into two or more separate components,and still be within the scope of the present invention.

Referring to FIG. 5, there is shown a flow diagram representing anexample operation (500) of the economizer controller. In particular,there is presented a method of an economizer controller 210 for managingeconomizer controller outputs in the form of output signals (270). Theeconomizer controller 210 receives multiple incoming control signals, inthe form of input signals 250 (for example, Y1 In, Y2 In, Y3 In, and Y4In), from an input device 220 (502). An example of the input device is,but is not limited to, a thermostat of an HVAC unit or environmentalcontrol system. Each incoming control signal of the multiple incomingcontrol signals is associated with a corresponding compressor of themultiple compressors. The compressor may be a compressor for cooling, acompressor for heating, or a combination cooling-compressor for heating.

The economizer controller 210 may execute one or more preliminaryactions before remapping the received input signals to rerouted outputsignals. For some embodiments, the economizer controller 210 maydetermining whether outside environmental air is suitable for freecooling (504). The economizer controller 210 may assign free cooling tobe a primary stage of cooling, in which free cool outside air intake maybe modulated with damper and fan speed (506), in response to determiningthat outside environmental air is suitable for free cooling. Free coolmay be a “virtual compressor” that uses outside air intake to cool aspace or area. On the other hand, the economizer controller 210 maysimply allow the cooling demand to transpass in response to determiningthat the outside environmental air is not suitable for free cooling(508). For some embodiments, the economizer controller 210 may determinewhether a cooling lockout is due to a detected low outside environmentaltemperature (510). The economizer controller 210 may inactivatemechanical cooling (512) in response to determining that the coolinglockout is due to the low outside environmental temperature. On theother hand, the economizer controller 210 may just calculate themechanical cooling demand (514) in response to determining that thecooling lockout is not due to the low outside environmental temperature.

The economizer controller 210 determines whether to remap the receivedinput signals to rerouted output signals (516). The rotation process maybe executed on a predetermined periodic basis, based on a determine timeschedule, or in response to a user action (such as, a signal from a userinterface).

In response to determining that the received input signals are to beremapped to the rerouted output signals (516), the rotation mode isinitiated by the economizer controller 210 (518) in which the inputsignals 250 are collected and prepared for analysis. For someembodiments, a setpoint for the rotation mode determines whether and/orwhen to execute a sorting logic to alter or otherwise change a priorityorder of some or all of the compressors. The sorting logic determinesthe priority (lead-lag) order based on run time, or cycling times atreal time or at the time when a sorting command is initiated.Accordingly, an altered association of at least some of the multipleincoming control signals to a different compressor of the multiplecompressors is generated based on a predetermined criteria (520). Thepredetermined criteria may include a run time count, a cycle count, or acombination of the run time and cycle counts for the multiplecompressors.

In response to executing the sorting logic (520) in which the coolingand/or heating demand from the thermostat is remapped to the coolingand/or heating command to the HVAC unit or rooftop unit, the economizercontroller 210 operates the compressors based on the updated compressorpriority (522). For example, the original priority order [Y1-Out,Y2-Out, Y3-Out, Y4-Out] may be adjusted to a different one with theleast run compressor in the first priority, the second least runcompressor in the second priority, etc., or with the least cycledcompressor in the first priority, the second least cycled compressor inthe second priority, etc. For some embodiments, the least run/cycledcompressor may be the first to run thus have the most chance to run,thus balancing the run times among the multiple compressors over time.

In response to determining that the received input signals are not to beremapped to the rerouted output signals (516), the economizer controller210 may execute, or schedule to execute, a predefined rotation plan(regardless of the sorting algorithm) with predefined rules and/orpredetermined compressor priority. For example, the prior leadcompressor may be one of the present lag compressor, and one of theprior lag compressors may be the present lead compressor.

In response to operating the compressors, whether based on the updatedcompressor priority (522) or not (524), the economizer controller 210sends output control signals based on the altered association to acontrol circuit associated with the compressors (526). An example of thecontrol circuit is, but is not limited to, a terminal board of the HVACunit or rooftop unit. Thereafter, the economizer controller 210 mayterminate the example operation (500) or update one or more run timecounters or cycle counters (530) and continue execute the sorting logic(520).

Referring to FIG. 6, there is shown an abstract view representing anexample operational information 600 about cooling and/or heatingcomponents associated with the economizer controller 210. The exampleoperational information 600 indicates that the first compressor has astatus Cmpr.CC1 of “Off” (602), a cycle count Cmpr.CC1Cnt.Cnt of “93”(604), and a run time count Cmpr.CC1-Elapsed/ActiveHour of “21 h” (606).Other properties of the first compressor indicated by the exampleoperational information 600 include nominal horsepower (608),kilowatt-hour count (610), and cycle count reset (612). Similarly, theexample operational information 600 indicates that the second compressorhas a status Cmpr.CC2 of “Off” (614), a cycle count Cmpr.CC2Cnt.Cnt of“15” (616), and a run time count Cmpr.CC1-Elapsed/ActiveHour of “2 h”(618), and other properties of the second compressor indicated by theexample operational information 600 include nominal horsepower (620),kilowatt-hour count (622), and cycle count reset (624). Accordingly, forthe first and second compressors represented by the example operationalinformation 600, the cycle count of the first compressor is higher thanthe cycle count of the second compressor, so the priority of the firstcompressor may be raised and the priority of the second compressor maybe reduced. Similarly, the run time count of the first compressor ishigher than the run time count of the second compressor, so the priorityof the first compressor may be raised and the priority of the secondcompressor may be reduced. Based on this example, the first and secondcompressors may be rotated in order balance their usage and increase thelongevity of the associated HVAC unit or rooftop unit.

Those skilled in the art will recognize that, for simplicity andclarity, the full structure and operation of all data processing systemssuitable for use with the present disclosure are not being depicted ordescribed herein. Also, none of the various features or processesdescribed herein should be considered essential to any or allembodiments, except as described herein. Various features may be omittedor duplicated in various embodiments. Various processes described may beomitted, repeated, performed sequentially, concurrently, or in adifferent order. Various features and processes described herein can becombined in still other embodiments as may be described in the claims.

It is important to note that while the disclosure includes a descriptionin the context of a fully functional system, those skilled in the artwill appreciate that at least portions of the mechanism of the presentdisclosure are capable of being distributed in the form of instructionscontained within a machine-usable, computer-usable, or computer-readablemedium in any of a variety of forms, and that the present disclosureapplies equally regardless of the particular type of instruction orsignal bearing medium or storage medium utilized to actually carry outthe distribution. Examples of machine usable/readable or computerusable/readable mediums include: nonvolatile, hard-coded type mediumssuch as read only memories (ROMs) or erasable, electrically programmableread only memories (EEPROMs), and user-recordable type mediums such asfloppy disks, hard disk drives and compact disk read only memories(CD-ROMs) or digital versatile disks (DVDs).

Although an example embodiment of the present disclosure has beendescribed in detail, those skilled in the art will understand thatvarious changes, substitutions, variations, and improvements disclosedherein may be made without departing from the spirit and scope of thedisclosure in its broadest form.

What is claimed is:
 1. A controller for managing of economizer outputscomprising: an input component configured to receive a plurality ofincoming control signals from an input device, each incoming controlsignal of the plurality of incoming control signals being associatedwith a corresponding compressor of a plurality of compressors; aprocessor configured to generate an altered association of at least someof the plurality of incoming control signals to a different compressorof the plurality of compressors based on a predetermined criteria; andan output component configured to send a plurality of output controlsignals based on the altered association to a control circuit associatedwith the plurality of compressors.
 2. The controller as described inclaim 1, wherein the input device is a thermostat and the controlcircuit is a terminal board of an HVAC unit or rooftop unit.
 3. Thecontroller as described in claim 1, wherein the compressor is at leastone of a compressor for cooling and a compressor for heating.
 4. Thecontroller as described in claim 1, wherein the predetermined criteriaincludes at least one of a run time count or a cycle count for theplurality of compressors.
 5. The controller as described in claim 1,wherein the processor updates at least one of run time counter or cyclecounter in response to the output component sending the plurality ofoutput control signals.
 6. The controller as described in claim 1,wherein the economizer controller assigns free cooling to a primarystage of cooling in response to determining that outside environmentalair is suitable for free cooling.
 7. The controller as described inclaim 1, wherein the economizer controller inactivates mechanicalcooling in response to determining that a cooling lockout is due to lowoutside environmental temperature.
 8. A method of a controller formanaging economizer outputs, the method comprising: receiving aplurality of incoming control signals from an input device, eachincoming control signal of the plurality of incoming control signalsbeing associated with a corresponding compressor of a plurality ofcompressors; generating an altered association of at least some of theplurality of incoming control signals to a different compressor of theplurality of compressors based on a predetermined criteria; and sendinga plurality of output control signals based on the altered associationto a control circuit associated with the plurality of compressors. 9.The method as described in claim 8, wherein the input device is athermostat and the control circuit is a terminal board of an HVAC unitor rooftop unit.
 10. The method as described in claim 8, wherein thecompressor is at least one of a compressor for cooling and a compressorfor heating.
 11. The method as described in claim 8, wherein thepredetermined criteria includes at least one of a run time count or acycle count for the plurality of compressors.
 12. The method asdescribed in claim 8, further comprising updating at least one of runtime counter or cycle counter.
 13. The method as described in claim 8,further comprising: assigning free cooling to a primary stage of coolingin response to determining that outside environmental air is suitablefor free cooling.
 14. The method as described in claim 8, furthercomprising: inactivating mechanical cooling in response to determiningthat a cooling lockout is due to low outside environmental temperature.15. A non-transitory computer readable medium including executableinstructions which, when executed, causes at least one processor tomanage rotation of economizer outputs by: receiving a plurality ofincoming control signals, each incoming control signal of the pluralityof incoming control signals being associated with a correspondingcompressor of a plurality of compressors; generating an alteredassociation of at least some of the plurality of incoming controlsignals to a different compressor of the plurality of compressors basedon a predetermined criteria; and sending a plurality of output controlsignals based on the altered association.
 16. The non-transitorycomputer readable medium as described in claim 15, wherein the inputdevice is a thermostat and the control circuit is a terminal board of anHVAC unit or rooftop unit.
 17. The non-transitory computer readablemedium as described in claim 15, wherein the compressor is at least oneof a compressor for cooling and a compressor for heating.
 18. Thenon-transitory computer readable medium as described in claim 15,further comprising updating at least one of run time counter or cyclecounter, wherein the predetermined criteria includes at least one of arun time count or a cycle count for the plurality of compressors. 19.The non-transitory computer readable medium as described in claim 15,further comprising: assigning free cooling to a primary stage of coolingin response to determining that outside environmental air is suitablefor free cooling.
 20. The non-transitory computer readable medium asdescribed in claim 15, further comprising: inactivating mechanicalcooling in response to determining that a cooling lockout is due to lowoutside environmental temperature.